Five years of support have been requested to study the immunological mechanisms involved in the demyelination induced by Theiler's murine encephalomyelitis virus. This is one of two well accepted animal model systems to study the process of demyelination observed in human MS. However the evidence sugesting a viral etiology in MS is largely circumstantial. The applicant has presented some good preliminary evidence which includes the construction and selection of recombinant lambda gt11 clones with TMEV inserts. Approximately 200 clones expressing correct reading frame of the inserts were selected using polyclonal rabbit antibodies specific for whole TMEV and/or the major individual viral capsid proteins. Fifty-nine of the clones were used to identify viral epitopes recognized by serum antibodies from susceptible and resistant mouse strains. The pattern of reactivity differed depending on the strain of mice. However certain fusion proteins were commonly reactive with all sera tested. Furthermore, using a monoclonal antibody (8C) raised against TMEV, fusion proteins from nine clones were identified which also reacted strongly with antibodies from both susceptible and resistant mice. Initial results suggest that the reactivity of these nine clones may represent an identical epitope and the overall number of conformation-independent dominant epitopes may be extremely limited. To determine the regions of TMEV reflected in the fusion protein inserts, the nucleotide sequences of the insert DNA in the recombinant lambda gt11 clones were determined. Using sera from both susceptible and resistant mouse strains the applicant has begun to localize the predominant antibody epitopes. Finally some very preliminary data are presented from studies aimed at determining the possibility that the major antibody epitopes are also recognized as major T cell epitopes. The proposed studies are outlined in four related specific aims. These include (1) the further identification of conformation-independent epitopes recognized by antibodies, (2) the assessment of the role of antibodies specific for predominant viral epitopes in the demyelination process, (3) the determination of TMEV capsid epitopes recognized by T lymphocytes and, (4) the identification of T cell epitopes involved in TMEV-induced demyelination.